check if file exists

void MainWindow::startGame() {

    stats = Statsgen((ui->fileLine->text()).toUtf8().constData());

    QString filename = ui->fileLine->text();

    if(filename.isEmpty()){

        QMessageBox(QMessageBox::Critical, "File empty", "You have not provided a filename !").exec();

        return;

    }

    if(! QFile::exists(filename)){

        QMessageBox(QMessageBox::Critical, "No such file", "The file " + filename + " does not exist !").exec();

        return;

    }

    stats = Statsgen(filename.toUtf8().constData());

    if(ui->withcountButton->isChecked())

    {